The present invention relates to drilling apparatus and more particularly to mechanism for vibrating the core receiving tube as the drill string is being rotated.
At times, during core drilling operation, greater resistance to the core receiving tube slipping axially inwardly along the core as the cut is being cut is encountered than is desirable. Also, at times, during core drilling operation and more particularly when drilling in broken earth formations and sandy and/or gravel type formations, the core will become more packed along the inner peripheral wall of the core receiving tube than at the radial central part of the tube and/or the radial outer part of the tube will fill up while the central part of the tube is not filled.
U.S. Pat. No. 4,279,315 to Tibussek discloses a wire line core barrel inner tube assembly that includes a latch body mounting latches for movement into a latch seat to retain said assembly adjacent to the drill bit, and clutch dogs movable into grooves in the drill string to rotate the latch body with the drill string. The latch body is rotatable relative to the core receiving tube and as the latch body rotates, a hammer strikes an anvil to impart striking force that is applied to the core receiving tube.
U.S. Pat. No. 3,194,326 to Bodine discloses a coring tool for obtaining a core underwater and subjecting the tube to sonic vibrations for providing a force that, during the half cycle of elastic elongation of the elastic stem, results in the core receiving tube moving downwardly in the earth formation. Herbold, U.S. Pat. No. 3,049,185, discloses a link pivotally connected between spaced magnetic disks and the core receiving tube. The magnetic disks are magnetically attached to the radial inner surface of a drilling tube to be eccentric to the central axis of the drilling tube and are rotated to generate centrifugal forces that are said to decrease frictional resistance to drilling.
In order to make improvements in core drilling apparatus to facilitate the collection of a core sample, this invention has been made.